Flash lamp fixing device

Abstract

A flash lamp fixing with a simple structure, capable of obtaining an even distribution of high-level luminous energy over a large area on the surface of a paper sheet illuminated by a flash lamp. In the flash lamp fixing device, the half breadth L 1 of the aperture of the reflector is set so as to satisfy the equation V/T≧L 1 ≧V/T-L 2 /2, where V is the conveying speed of a paper sheet; T is the flash cycle of the flash lamp; L 1 is the half breadth of the aperture of the reflector; and L 2 is the length of an area in which fixing can be done by one flash of the flash lamp. Where θ 1 represents the included angle between a tangent which passes through one of aperture edges, being tangent to the flash lamp on the side of the aperture and the plane of the aperture; and θ 2 represents the included angle between a tangent which passes through the aperture edge, being tangent to a safety distance critical circle centered on the center of the flash lamp and a plane normal to the aperture plane, the tilt angles of the respective inclined face parts in relation to the plane normal to the aperture plane are set to be not less than θ 1 and not more than θ 2 .

What is claimed is: 
     
       1. A flash lamp fixing device comprising a flash lamp and a reflector which is so formed as to enclose the flash lamp except for an aperture formed at a side of the flash lamp, for reflecting part of light emitted from the flash lamp towards the aperture, wherein the equation   V/T≧L.sub.1 ≧V/T-L.sub.2 /2     holds, where V is the conveying speed of a paper sheet; T is the flash cycle of the flash lamp; L 1  is the half breadth of the aperture of the reflector; and L 2  is the length of an area in which fixing can be done by one flash of the flash lamp.   
     
     
       2. A flash lamp fixing device comprising a flash lamp and a reflector which is so formed as to enclose the flash lamp except for an aperture formed at a side of the flash lamp, for reflecting part of light emitted from the flash lamp towards the aperture, wherein the reflector is formed with a pair of inclined face parts which are disposed on both lateral sides of the flash lamp, inclining like an unfolded fan widened towards a paper sheet and a back face part disposed intermediate the inclined face parts and behind the flash lamp, and   wherein where θ 1  represents the included angle between a tangent which passes through one of aperture edges of the reflector, being tangent to the flash lamp on the side of the aperture and the plane of the aperture; and θ 2  represents the included angle between a tangent which passes through the aperture edge, being tangent to a safety distance critical circle and a plane normal to the aperture plane, the safety distance critical circle with centre at the centre of the flash lamp being an area where the leakage of electric charge does occur, the tilt angles of the respective inclined face parts in relation to the plane normal to the aperture plane are set to be not less than θ 1  and not more than θ 2 .   
     
     
       3. The flash lamp fixing device as claimed in claim 2, wherein each of the inclined face parts has a posterior end which is located closer to one of the aperture edges than the intersection of the oblique line of the inclined face part and a circle which encloses the flash lamp being tangent thereto and is centered on a middle point between the centre of the flash lamp and the aperture edge. 
     
     
       4. The flash lamp fixing device as claimed in claim 3, wherein the back face part is configured to be a flat face which is parallel with the aperture plane, being tangent to the safety distance critical circle or passing outside the safety distance critical circle. 
     
     
       5. The flash lamp fixing device as claimed in claim 3, wherein the back face part is configured to be a curved passes outside the safety distance critical circle. 
     
     
       6. The flash lamp fixing device as claimed in claim 3, wherein the back face part is configured to be a bent face which is tangent to the safety distance critical circle or passes outside the safety distance critical circle. 
     
     
       7. The flash lamp fixing device as claimed in claim 2, wherein the back face part is configured to be a flat face which is parallel with the aperture plane, being tangent to the safety distance critical circle or passing outside the safety distance critical circle. 
     
     
       8. The flash lamp fixing device as claimed in claim 2, wherein the back face part is configured to be a curved face which is tangent to the safety distance critical circle or passes outside the safety distance critical circle. 
     
     
       9. The flash lamp fixing device as claimed in claim 2, wherein the back face part is configured to be a bent face which is tangent to the safety distance critical circle or passes outside the safety distance critical circle. 
     
     
       10. The flash lamp fixing device as claimed in claim 9, wherein the bent face comprises an angled face projecting in a direction opposite to the aperture plane. 
     
     
       11. The flash lamp fixing device as claimed in claim 9, wherein the bent face comprises an angled face projecting in a direction opposite to the aperture plane and flat faces which continue from both sides of the angled face, being parallel with the aperture plane. 
     
     
       12. The flash lamp fixing device as claimed in claim 9, wherein the bent face comprises a flat face parallel with the aperture plane and slant faces which continue from both sides of the flat face. 
     
     
       13. The flash lamp fixing device as claimed in claim 9, wherein the bent face comprises a curved face along an are of the safety distance critical circle and flat faces which continue from both sides of the curved face, being parallel with the aperture plane. 
     
     
       14. The flash lamp fixing device as claimed in claim 2, wherein the tilt angles of the inclined face parts are set to θ 2 , each of the inclined face parts has a posterior end which is set at the point of contact of a tangent to the safety distance critical circle, and the back face part is a curved face along an arc of the safety distance critical circle. 
     
     
       15. The flash lamp fixing device as claimed in any one of claims 2, 3 or 7-14, wherein a plurality of flash lamps are disposed in parallel with each other, being a specified distance separated from the aperture plane and the inclined face parts are disposed outside the outermost flash lamps. 
     
     
       16. A flash lamp fixing device comprising a flash lamp and a reflector which is so formed as to enclose the flash lamp except for an aperture formed at a side of the flash lamp, for reflecting part of light emitted from the flash lamp towards the aperture, wherein the reflector is formed with a pair of inclined face parts which are disposed on both lateral sides of the flash lamp, inclining like an unfolded fan widened towards a paper sheet and a back face part disposed intermediate the inclined face parts and behind the flash lamp, and   wherein the back face part is composed of two angled faces which are symmetrically placed and caved in a direction toward the aperture plane.   
     
     
       17. A flash lamp fixing device comprising a flash lamp and a reflector which is so formed as to enclose the flash lamp except for an aperture formed at a side of the flash lamp, for reflecting part of light emitted from the flash lamp towards the aperture, wherein the reflector is formed with a pair of inclined face parts which are disposed on both lateral sides of the flash lamp, inclining like an unfolded fan widened towards a paper sheet and a back face part disposed intermediate the inclined face parts and behind the flash lamp, and   wherein at least the back face part of the reflector is formed in a bellows-like shape in which angled faces projecting in a direction opposite to the aperture plane and caving in a direction towards the aperture plane are successively aligned.   
     
     
       18. A flash lamp fixing device comprising a flash lamp and a reflector which is so formed as to enclose the flash lamp except for an aperture formed at a side of the flash lamp, for reflecting part of light emitted from the flash lamp towards the aperture, wherein the reflector is formed with a pair of inclined face parts which are disposed on both lateral sides of the flash lamp, inclining like an unfolded fan widened towards a paper sheet and a back face part disposed intermediate the inclined face parts and behind the flash lamp, and   wherein at least the back face part of the reflector is formed to include a plurality of projections or concaves disposed regularly, each of which assumes the form of a polygonal pyramid.   
     
     
       19. A flash lamp fixing device comprising a flash lamp and a reflector which is so formed as to enclose the flash lamp except for an aperture formed at a side of the flash lamp, for reflecting part of light emitted from the flash lamp towards the aperture, wherein the flash lamp is disposed in a position deviated from the centre of the width of the aperture of the reflector towards the downstream of a paper conveying direction, and   wherein where the conveying speed of a paper sheet is represented by V; the flash cycle of the flash lamp is represented by T; and the width of the aperture of the reflector is represented by L 3 , the equation   L.sub.3 ≧2V/T     holds.     
     
     
       20. The flash lamp fixing device as claimed in claim 19, wherein the reflector is formed with a pair of inclined face parts which are disposed on both lateral sides of the flash lamp, inclining like an unfolded fan widened towards a paper sheet and a back face part disposed intermediate the inclined face parts and behind the flash lamp, and wherein the tilt angle of the inclined face part at the upstream of the paper conveying direction is gentler than that of the inclined face part at the downstream of the paper conveying direction.